I’m trying to get better at proportions and general anatomy. Aside from that, do I approach these poses by drawing the Loomis stick figure? Or by following the most prominent lines (Currently doing this) Or negative space drawing? Or boxing in the figure?

I’m also kinda stuck with wanting to do fluid line motion and correct bone structure.

Hello Tinayashami, your proportions already look great in my opinion. I would try prominent lines, basic shapes, negative space and boxing the figure. I think each one would make you think about how you approach your work in a different way. What might work for you is getting the anatomy right first (correct bone structure). After everything is in the right place see what parts of the drawing you can exaggerate. Look for straight lines and opposing curves. You can also adjust the pose. If you think it would look better if the arm was raised more, feel free to push the pose even if it doesn't match the image exactally. It also looks like you are using a graphite pencil. If you do your initial work in blue pencil it would allow you to be a little messier initially and be able to clean it up with the graphite pencil after. That will also allow you to be more fluid with your lines without having to worry about the structure. I hope that helps you.

This is the blue pencil I like to use. Its eraser is actually good and doesn't carve into your paper like a lot of the other non photo blues.